全文获取类型
收费全文 | 318篇 |
免费 | 23篇 |
专业分类
林业 | 3篇 |
农学 | 9篇 |
41篇 | |
综合类 | 94篇 |
农作物 | 60篇 |
水产渔业 | 2篇 |
畜牧兽医 | 120篇 |
园艺 | 4篇 |
植物保护 | 8篇 |
出版年
2023年 | 5篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 13篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1968年 | 3篇 |
1959年 | 2篇 |
1956年 | 2篇 |
1913年 | 2篇 |
1893年 | 2篇 |
排序方式: 共有341条查询结果,搜索用时 17 毫秒
51.
52.
K. G. Haynes D. H. Lambert B. J. Christ D. P. Weingartner D. S. Douches J. E. Backlund G. Secor W. Fry W. Stevenson 《American Journal of Potato Research》1998,75(5):211-217
Changes in the fungal pathogenPhytophthora infestans in the United States pose a significant threat to potato production. Sources of resistance to these new genotypes of P.infestans need to be identified for potato breeders to have parental materials for crossing, and the phenotypic stability of late blight resistance in these potato clones needs to be determined. Sixteen potato clones which reportedly have some resistance to late blight were evaluated at eight locations: Florida (FL), Maine (ME), Michigan (MI), Minnesota (MN), North Dakota (ND), New York (NY), Pennsylvania (PA) and Wisconsin (WI) in 1996. Percent infected foliage was recorded at approximately weekly intervals following the onset of the disease at each location. Area under the disease progress curve (AUDPC) was calculated. Clones were ranked for mean AUDPC within location and the nonparametric stability statistics, mean absolute rank differences and variance of the ranks, were analyzed for phenotypic stability. Neither of these statistics was significant, indicating a lack of genotype x environment interaction on the rankings of these clones across locations in 1996. The four clones with lowest AUDPC scores were U.S. clones AWN86514-2, B0692-4, B0718-3 and B0767-2. These clones should be useful parental materials for breeders seeking to incorporate genes for late blight resistance into potatoes. 相似文献
53.
54.
Mohammad Redwanur Rahman Md. Asaduzzaman Md. Mahiuddin Zahangir SM Rashadul Islam Sk Ahmad‐Al Nahid Durin Akter Jahan Yahia Mahmud Mohammed Nurul Absar Khan 《Aquaculture Research》2020,51(6):2555-2572
Soft‐shell crab, a newly moulted crab having non‐calcified and hydrated soft exoskeleton, farming has been increasing tremendously in recent years throughout the world due to its high market price and consumer preferences. However, high aggressiveness and cannibalistic behaviour of mud crab limit its culture to an individual chamber system which ultimately makes the soft‐shell mud crab farming space and labour‐intensive. Therefore, the aim of this study was to improve the efficiency of soft‐shell crab production by autotomy of the claw and/or walking legs to reduce the moulting duration and intensify the culture system through double stocking in the existing individual chamber culture system. To achieve our objectives, a series of experiment were conducted at both indoor and on‐farm levels by removing the claw and/or walking legs of Scylla olivacea for two consecutive moulting cycles. Results showed that both claw ablation significantly (p < .01) shortened the moulting duration and increased the carapace width, weight gain, specific growth rate, feeding efficiency and yield parameter compared to the non‐ablated crabs more prominently at 1st moulting than the 2nd moulting in both indoor and on‐farm trials. Ablation of all walking legs while keeping the claw intact did not significantly influence (p > .05) the moulting duration and carapace width, but significantly (p < .01) improved the specific growth rate, weight gain, feeding efficiency and yield parameters at 1st moulting compared to the non‐ablation and unilateral three walking leg ablation groups. However, ablation of all appendages (both claw and walking legs) showed significant (p < .01) improvements of carapace width, weight gain, specific growth rate, feeding efficiency and yield parameters, and shortened the moulting duration up to 23 days from 34 days during 1st moulting and up to 27 days from 40 days at 2nd moulting. The survivals of different autotomized mud crabs were statistically non‐significant (p > .05) to the non‐autotomized crabs in various indoor and on‐farm trials. Besides improving the production performances, ablation of bilateral claw and all appendages allowed to double the stocking density in the existing individual chamber‐based soft‐shell crab farming that enhanced the production about threefold higher than the existing individual chamber‐based culture system. Finally, our results suggest that autotomy could be a promising technology for the commercial farming of soft‐shell mud crab in near future. 相似文献
55.
Recently proposals have been made in both Europe and North America to try to radically change potato breeding strategy from a tetraploid, heterozygous crop to a diploid inbred crop. As part of that effort, clones from the long-day adapted, late blight resistant diploid hybrid Solanum phureja – S. stenotomum population were selfed to begin the process of developing inbred lines. In March of 2016 and 2017, 42 diploid clones from the above-mentioned population were selfed in the greenhouse in Beltsville, MD. In 2016 and 2017, 10 and 13 clones failed to flower, respectively. Among the remaining clones, 716 pollinations were made in 2016, resulting in 57 fruit from 17 clones, and 3742 seeds; 801 pollinations were made in 2017, resulting in 34 fruit from 12 clones, and 1903 seeds. Nine clones were successfully selfed both years. Percent successful selfs was significantly higher in 2016 (7.96%) than in 2017 (4.24%). The most prolific clones in 2016 were BD1241–1 (34% successful selfs, 1090 seed), BD1218–3 (25% successful selfs, 638 seed), BD1215–1 (5% successful selfs, 411 seed), BD1243–1 (23% successful selfs, 232 seed). In contrast, the most prolific clones in 2017 were BD1230–2 (25% successful selfs, 537 seed), BD1203–3 (23% successful selfs, 391 seed), and BD1229–1 (11% successful selfs, 388 seed). These results indicate that there is sufficient self-compatibililty in this population to generate large numbers of inbred individuals, but that genotype x environment interactions are large. Attempts to generate selfed seed should be made over several years to maximize the genetic base of the selfed population. 相似文献
56.
57.
Australian surveillance for avian influenza viruses in wild birds between July 2005 and June 2007 总被引:1,自引:1,他引:0
L Haynes E Arzey C Bell N Buchanan G Burgess V Cronan C Dickason H Field S Gibbs PM Hansbro T Hollingsworth AC Hurt P Kirkland H McCracken J O'Connor J Tracey J Wallner S Warner R Woods C Bunn 《Australian veterinary journal》2009,87(7):266-272
Objective To identify and gain an understanding of the influenza viruses circulating in wild birds in Australia.
Design A total of 16,303 swabs and 3782 blood samples were collected and analysed for avian influenza (AI) viruses from 16,420 wild birds in Australia between July 2005 and June 2007. Anseriformes and Charadriiformes were primarily targeted.
Procedures Cloacal, oropharyngeal and faecal (environmental) swabs were tested using polymerase chain reaction (PCR) for the AI type A matrix gene. Positive samples underwent virus culture and subtyping. Serum samples were analysed using a blocking enzyme-linked immunosorbent assay for influenza A virus nucleoprotein.
Results No highly pathogenic AI viruses were identified. However, 164 PCR tests were positive for the AI type A matrix gene, 46 of which were identified to subtype. A total of five viruses were isolated, three of which had a corresponding positive PCR and subtype identification (H3N8, H4N6, H7N6). Low pathogenic AI H5 and/or H7 was present in wild birds in New South Wales, Tasmania, Victoria and Western Australia. Antibodies to influenza A were also detected in 15.0% of the birds sampled.
Conclusions Although low pathogenic AI virus subtypes are currently circulating in Australia, their prevalence is low (1.0% positive PCR). Surveillance activities for AI in wild birds should be continued to provide further epidemiological information about circulating viruses and to identify any changes in subtype prevalence. 相似文献
Design A total of 16,303 swabs and 3782 blood samples were collected and analysed for avian influenza (AI) viruses from 16,420 wild birds in Australia between July 2005 and June 2007. Anseriformes and Charadriiformes were primarily targeted.
Procedures Cloacal, oropharyngeal and faecal (environmental) swabs were tested using polymerase chain reaction (PCR) for the AI type A matrix gene. Positive samples underwent virus culture and subtyping. Serum samples were analysed using a blocking enzyme-linked immunosorbent assay for influenza A virus nucleoprotein.
Results No highly pathogenic AI viruses were identified. However, 164 PCR tests were positive for the AI type A matrix gene, 46 of which were identified to subtype. A total of five viruses were isolated, three of which had a corresponding positive PCR and subtype identification (H3N8, H4N6, H7N6). Low pathogenic AI H5 and/or H7 was present in wild birds in New South Wales, Tasmania, Victoria and Western Australia. Antibodies to influenza A were also detected in 15.0% of the birds sampled.
Conclusions Although low pathogenic AI virus subtypes are currently circulating in Australia, their prevalence is low (1.0% positive PCR). Surveillance activities for AI in wild birds should be continued to provide further epidemiological information about circulating viruses and to identify any changes in subtype prevalence. 相似文献
58.
Richard J. Haynes 《Soil Science and Plant Nutrition》2018,64(4):535-541
The effects of pH on the adsorption of silicate and phosphate, either singly or in competition, by two acid soils were investigated. Both soils adsorbed two to three times more P than Si and adsorption isotherms at pH 5.0, 5.5, 6.0 and 6.5 showed that increasing pH greatly increased Si adsorption but decreased that of P. Silicate adsorption was very low below pH 5.0, increased rapidly up to pH 9–10 before decreasing again. Adsorption of P was at a maximum at pH 2.0, decreased slowly up to pH 7.0 and then more rapidly above pH 7.0. When Si and P were added at equimolar concentrations, the presence of P decreased Si adsorption between pH 6.0 and 8.0 while the presence of Si decreased P adsorption in the pH region 6.0 and 11. Addition of calcium silicate at rates equivalent to 300, 600 and 1200 kg Si ha?1 resulted in a progressive increase in soil pH. Separate samples of soil were treated with Ca(OH)2 to give the same pH values so that the effect of Si could be identified. The highest rate of Si (1200 kg ha?1 which gave a pH of 6.5) caused a significant decrease in P adsorption (as determined by adsorption isotherms) and an increase in resin-extractable P but the lower rates had little effect. Addition of P to the soil as calcium phosphate at rates equivalent to 30, 60 and 100 kg P ha?1 all caused a decrease in Si adsorption capacity and an increase in CaCl2-extractable Si. It was concluded that the strategy of adding Si to lower P requirements in acid soils is not likely to be effective while addition of fertilizer P may well lower Si adsorption and promote Si desorption and its increased mobility. 相似文献
59.
60.
SM Gonzalez CB da Silva AG Lindquist I Bufalo F Morotti LA Lisboa M Seneda 《Reproduction in domestic animals》2017,52(5):836-841
The goal of this study was to determine the distribution of pre‐antral follicles in the ovarian parenchyma of mares. For Experiment 1, each ovary was cut longitudinally at the greater curvature, performing two hemiovaries. After that, six fragments from each hemiovary were obtained, resulting in 12 fragments, which were divided into the innermost region of the parenchyma, the middle region and the outermost region. All the three obtained sections were cut transversally to obtain two fragments from each one. For Experiment 2, each ovary also submitted to a longitudinal cut on the greater curvature, forming two hemiovaries. Each hemiovary was sectioned into four symmetrical fragments, resulting in eight fragments per ovary. The fragments were related as being near to or far from the ovulatory fossa. The fragments of both experiments were immediately fixed in Carnoy for 12 hr and kept in 70% ethanol for 24 hr. Follicles were classified according to the stages of development and for morphological integrity according to oocyte morphology and granulosa cells. After the histological assessment, a total of 1,130 follicles were visualized from Experiment 1, being 1,054 (93.3%) primordial follicles and 76 (4.7%) follicles in development. The innermost region had the highest percentage of pre‐antral follicles compared to the other regions (p < .05). The middle and outermost regions showed higher percentages of intact primordial and developing follicles than the innermost region (p < .05). Considering Experiment 2, 938 follicles were found, being 894 (95.3%) primordial and 44 (4.7%) follicles in development. The region near the ovulatory fossa presented higher (58.7%; 551 of 938) follicular concentration compared to the region far from the ovulatory fossa (41.3%; 387 of 938; p < .05). As a conclusion, distribution of pre‐antral follicles in the equine ovary has a specific pattern through the parenchyma. Also, the follicular integrity differed in the studied ovarian areas. 相似文献